This invention relates to a tool and particularly one in which an interchangeable insert is held in operative position by a holder assembly. Devices of this general nature are known and one construction thereof which has met with particular success is described in applicant's previous patent U.S. Pat. No. 3,545,060 issued Dec. 8, 1970.
The device disclosed in that patent includes a body 12 provided with a recess 18 at the forward end thereof on which an insert 44 having at least one cutting surface 46 is positioned thereon with regard to an alignment means 74. A wedge 56 is disposed between the insert and an inclined wedging surface 24 of the body 12. It may thus be seen that the front and rear wedging surfaces of the wedge are adapted to respectively contact the rear surface 52 of the insert and the inclined wedging surface 24 of the body respectively in face-to-face contact. Such contact on occasion can, however, result in frictional blocking or taper lock between the respective sliding surfaces such that the wedge may become hung up or locked by such frictional contact and will not travel its full distance to insure proper positioning of the insert. Such taper locking can occur when two generally highly polished surfaces are placed in intimate sliding contact with each other. The citation and discussion of applicant's above-identified patent constitutes applicant's Prior Art Statement; and in that regard, a copy of such patent is included with this application.
It is accordingly a primary object of the present invention to provide a tool of the above-indicated type wherein such undesirable taper locking is prevented.
A further object of the present invention is the provision of a tool of the immediately aforementioned type in which interchangeable inserts may be properly positioned with regard to a tool body by means of a wedge acting upon a back locating surface of the insert in substantial line contact therewith.
These and other objects of the present invention are accomplished by a provision of an upwardly extending step at adjacent rear portions of the inclined wedging surface which delineates the rear wall of the recess. The position of the step is such that rear bottom wall surfaces of the wedge are adapted to abut or rest upon it. Thereafter, upon further downward travel of the wedge in the opening between the insert and the body, forward portions of the wedge are downwardly tilted into substantially line contact with the back locating surface of the insert. This prevents extensive sliding contact between the opposed and generally highly polished surfaces of the insert and wedge and thus avoids any possible taper lock between them.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawing.